1. Field
The present invention relates to a washing machine, and, more particularly, to a washing machine including a washing tub that is capable of decreasing the damage to laundry and improving the washing efficiency.
2. Description of the Related Art
Korean Patent Publication No. 2006-107036 discloses a washing machine including a drum-type washing tub rotatably mounted in a water tub. Inside the washing tub is mounted a plurality of lifters to lift and drop laundry during the rotation of the washing tub. In the circumference of the washing tub are formed a plurality of spin-drying holes to drain the water.
In this washing machine, the washing tub is rotated at high speed, while water in the water tub is drained during the spin-drying operation of the washing machine. With the high-speed rotation of the washing tub, laundry is brought into tight contact with the inner surface of the washing tub due to a centrifugal force, and water contained in the laundry is discharged through the spin-drying holes due to the centrifugal force.
As shown in FIG. 1, each spin-drying hole 2 formed in a washing tub 1 of such a washing machine is constructed in a conical shape whose diameter is gradually reduced from an inner surface to an outer surface of the washing tub 1. Each spin-drying hole 2 is deformed in a curved shape from an inner side to an outer side of the washing tub 1 with the result that each spin-drying hole 2 has a height h greater than the thickness of the washing tub 1. Each spin-drying hole 2 has a diameter of approximately 3.5 mm. Approximately 2000 spin-drying holes 2 are formed in the circumference of the washing tub 1. The size and number of the spin-drying holes 2 may be changed depending upon the washing tub 1.
When the spin-drying operation of the washing machine is operated at high speed, laundry 3 is brought into tight contact with the inner surface of the washing tub 1 due to a centrifugal force, as shown in FIG. 1. Consequently, when the laundry 3 is a soft material, portions of the laundry 3 adjacent to the spin-drying holes 2 may be introduced into the spin-drying holes 2 with the result that the laundry 3 becomes deformed. Specifically, a plurality of protrusions 3a may be formed at the surface of the laundry 3. This is because the portions of the laundry 3 adjacent to the spin-drying holes 2 are not supported, and the laundry 3 is deformed due to the flow of wash water drained out of the washing tub 1 through the spin-drying holes 2.
Also, the inner surface of the washing tub 1 is flat. Consequently, the friction between the inner surface of the washing tub 1 and the laundry is small during the washing operation of the washing machine, with the result that the washing efficiency due to the friction is limited.
Furthermore, it is necessary to supply wash water to the water tub such that the laundry 3 in the washing tub is immersed in the wash water during the washing operation of the washing machine. Consequently, the wash water consumption of the washing machine is large.